Although still abundant at Cocos Island and other relatively pristine sites, grey reef sharks are susceptible to localized depletion due to their slow reproductive rate, specific habitat requirements, and tendency to stay within a certain area. The IUCN has assessed the grey reef shark as Near Threatened; this shark is taken by multispecies fisheries in many parts of its range and used for various products such as shark fin soup and fishmeal. Another threat is the continuing degradation of coral reefs from human development. There is evidence of substantial declines in some populations. Anderson et al. (1998) reported, in the Chagos Archipelago, grey reef shark numbers in 1996 had fallen to 14% of 1970s levels. Robbins et al. (2006) found grey reef shark populations in Great Barrier Reef fishing zones had declined by 97% compared to no-entry zones (boats are not allowed). In addition, no-take zones (boats are allowed but fishing is prohibited) had the same levels of depletion as fishing zones, illustrating the severe effect of poaching. Projections suggested the shark population would fall to 0.1% of pre-exploitation levels within 20 years without additional conservation measures. One possible avenue for conservation is ecotourism, as grey reef sharks are suitable for shark-watching ventures, and profitable diving sites now enjoy protection in many countries, such as the Maldives.
Socially, they are mostly loners unless living in a threatening ecosystem. These are the first and the only species of sharks that are known to “sleep” on the ocean floor or within reef caves. It is believed that these sharks are not actually sleeping but merely resting. These sharks have actually been given the nickname “sleeping sharks” because of their habit of lying motionless at the sea bottom. This is a somewhat unusual and unique behavior of these sharks.
Despite sharks being portrayed as notorious aggressive animals, very few incidents have involved blacktip reef sharks, none being fatal. Still the importance of an apex predator is vital to a balanced and healthy ecosystem. Unfortunately, this species is very susceptible to reef gill netting. And sharks all around continue to be threatened by fishing pressure resulting in a decrease in many shark populations.
A heavy-bodied shark with a "typical" streamlined shape, the Caribbean reef shark is difficult to distinguish from other large requiem shark species. It usually measures 2–2.5 m (6.6–8.2 ft) long; the maximum recorded length is 3 m (9.8 ft) and the maximum reported weight is 70 kg (150 lb). The coloration is dark gray or gray-brown above and white or white-yellow below, with an inconspicuous white band on the flanks. The fins are not prominently marked, and the undersides of the paired fins, the anal fin, and the lower lobe of the caudal fin are dusky.
The Caribbean reef shark feeds on a wide variety of reef-dwelling bony fishes and cephalopods, as well as some elasmobranchs such as eagle rays (Aetobatus narinari) and yellow stingrays (Urobatis jamaicensis). It is attracted to low-frequency sounds, which are indicative of struggling fish. In one observation of a 2 m (6.6 ft) long male Caribbean reef shark hunting a yellowtail snapper (Lutjanus crysurus), the shark languidly circled and made several seemingly "half-hearted" turns towards its prey, before suddenly accelerating and swinging its head sideways to capture the snapper at the corner of its jaws. Young sharks feed on small fishes, shrimps, and crabs. Caribbean reef sharks are capable of everting their stomachs, which likely serves to cleanse indigestible particles, parasites, and mucus from the stomach lining.
Based on morphological similarities, Jack Garrick in 1982 grouped this species with the bignose shark (C. altimus) and the sandbar shark (C. plumbeus), while Leonard Compagno in 1988 placed it as the sister species of the grey reef shark (C. amblyrhynchos). A phylogenetic analysis based on allozyme data, published by Gavin Naylor in 1992, indicated that the Caribbean reef shark is the sister taxon to a clade formed by the Galapagos shark (C. galapagensis), dusky shark (C. obscurus), oceanic whitetip shark (C. longimanus), and the blue shark (Prionace glauca). However, more work is required to fully resolve the interrelationships within Carcharhinus.
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The Caribbean reef shark (Carcharhinus perezi) is a species of requiem shark, belonging to the family Carcharhinidae. It is found in the tropical waters of the western Atlantic Ocean from Florida to Brazil, and is the most commonly encountered reef shark in the Caribbean Sea. With a robust, streamlined body typical of the requiem sharks, this species is difficult to tell apart from other large members of its family such as the dusky shark (C. obscurus) and the silky shark (C. falciformis). Distinguishing characteristics include dusky-colored fins without prominent markings, a short free rear tip on the second dorsal fin, and tooth shape and number.
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